Gunfire control apparatus



J. P. WATSON GUNFIRE CONTROL APPARATUS Filed June 14, 1932 l/M M A5 W kas: we.

Patented Jan. 5, 1937 UNITED STATES PATENT OFFICE GUNFIRE CONTROLAPPARATUS Application June 14, 1932, Serial No. 617,071 In Great BritainJune 20, 1931 16 Claims.

This invention relates to gun fire control apparatus for use on a shipor other moving platform and has for its chief object to provide animproved device for determining the course and speed of a moving targetfrom the observed changes of range and bearing of the target, suchchanges being, of course, due to the movements of the target and themovements of own ship when they are moving at different speeds and ondifferent courses.

According to the present invention the device comprises means wherebythe rate of change of range and the rate of change of bearing determinedfrom averagers, plotters or other devices, have deducted therefrom therates due to the movement of own ship, and members moved in accordancewith the resultants (i. e. the rates due only to the movement of thetarget) cause to move over a target dial, wires, grids or the like thepoint of intersection of which indicates the course and speed of thetarget.

In order that the said invention may be clearly understood and readilycarried into effect, the same. will now be described more fully withreference to the accompanying drawing which shows diagrammatically aform of apparatus according to the invention.

A, B represent the aforesaid wires or grids movable at right angles toeach other over the face of a target dial C which carries the outline ofa ship (representing the target) and which is pro- I vided with a targetspeed scale C running longitudinally of the ship outline and with amovable target speed pointer C The wire A is herein termed the rangerate wire and the wire B is termed the linear bearing rate wire. Thedial C is operated by a target inclination shaft C (operated through adifferential gear C from a target inclination handle or knob C and ashaft N hereinafter referred to) and the pointer C is operated by atarget speed shaft C operated by a target speed handle or knob C". Thetarget inclination is the target course relative to the line of sight.The shaft'C also drives the rotary portion or disc of a target analyzerD (the details of which are explained in the specification of EnglishPatent No. 381,147) and the shaft C operates the crank pin D of thisanalyzer, the result being that this crank pin occupies a positioncorresponding radially and angularly to the position of the pointer CThe handles or knobs C C" are operated by hand to cause the pointer C tocoincide with the point of intersection of the wires A and B and in sodoing the sliding elements D, D of the target analyzer are properly set.The sliding element D whose position is a measure of the rate of changeof range due to the movement of the target operates through adifferential gear E a screwthreaded shaft A carrying a nut which sup- 5ports the range rate wire A, the differential gear E being controlled bya range rate tuning handle E. The total movement of the shaft A iscombined by means of a differential gear F with movement derived fromthe range 10 rate element F of own ship analyzer (similar to the targetanalyzer) and the resultant movement of a shaft G is in accordance withthe sum of the two rates of change, i. e. the rate of change. of rangedue to the known movements of own ship and the rate of change of rangedue to the target movements to be ascertained. The shaft G adjusts theposition of a ball carrier H relating to a variable speed gearcomprising a disc H driven at a constant speed and a roller H drivenfrom the disc through the balls of the carrier H in accordance with thechanging range. The movement of the. roller 1-! is combined with themovement of a range tuning handle H by means of a differential gear Hand a screwthreaded shaft H is operated in accordance with the resultantwhich is the range of the moment. The shaft H drives a range transmitter11 The outer end of this shaft H is screw-threaded and engaged with theholder of a pencil H which follows range indications marked on a rangeplotter H from a range finder, the pencil being caused to trace a curveof average range. The aforesaid shaft G has splined thereto ascrewthreaded sleeve G which is prevented from moving longitudinallywith respect to the pencil holder and operates a non-rotary nut Gcarrying a cursor G pivoted around the holder of the pencil H theposition of this cursor tangential to the curve of average rangerepresenting the rate of change of the range. In this manner the correctrange rate can be quickly found and set by means of the range ratetuning handle E. The inclination of the plot is proportional to the rateof change of range due to the movement of the target 5 and own ship, butthe rate component derived from own ship analyzer is not communicated tothe range rate wire A which only receives its motion from the range ratetuning handle E and the target analyzer D.

The sliding element D of the target analyzer D (the movement of thiselement being a measure of the rate of change of linear bearing due tothe movement of the target) operates a screwthreaded shaft B through adifferential gear K itUUE controlled by a bearing rate tuning handle K.This screw-threaded shaft moves the linear bearing rate wire B and themovement of the said shaft is combined by means of a differential gear Lwith movement derived from the linear bearing rate element L of own shipanalyzer and the resultant movement of a shaft M is in accordance withthe sum of the two linear bearing rates. This resultant movement iscombined with the range movement of the aforesaid shaft H in order toobtain the corresponding angular bearing rate, by means of a suitablemechanism M which moves a shaft M in accordance with this angularbearing rate. The sliding element D rotates the screw M through gearwheel M shaft M", clutch K and differentials K and L. The screw Moperates the radius arm M of a slider mechanism M the slider mechanismcomprising radius bar M and sliders M M The slider M is moved constantlyby a cam M rotated by a worm M and gear wheel M the worm M being rotatedby a shaft M driven with the screw H at a rate proportional to thepresent range. The slider M thus imparts a movement to the slider M theamount of movement being dependent upon the movement of the radius bar MThe slider M therefore receives the resultant of the movements of M andM which, of course, is proportional to the angular bearing rate, sincethe latter depends upon the range and linear bearing. This shaft Madjusts the position of a ball carrier N relating to a variable speedgear comprising a disc N driven at a constant speed and a roller Ndriven from the disc through the balls of the carrier in accordance withthe changing bearing angles. The movement of the roller N is combinedwith the movement of a bearing tuning handle N by means of adifferential gear N and a screw= threaded shaft N is driven inaccordance with the resultant. This shaft N moves a pencil N whichfollows bearing angle indications marked on a bearing plotter N from abearing finder, the pencil being caused to trace a curve of averagebearing. The pencils H and N are moved transversely across the plotterby the mechanism described, and are adjusted until they move at a rateto maintain the desired courses. The plotters H and N are moved(vertically with respect to the drawing) at a rate proportional to time.The aforesaid shaft M has a screwthreaded portion M which operates a nutM carrying a cursor M pivoted around the holder of the pencil N theposition of this cursor tangentiai to the curve of average bearingrepresenting the rate of change of the bearing. In this manner thecorrect bearing rate can be quickly found and set by means of thebearing rate tuning handle K. The rate of change of bearing is due tothe movement of the target and own ship, but the rate component derivedfrom own ship analyzer is not communicated to the bearing rate wire Bwhich only receives its motion from the bearing rate tuning handle K andthe target analyzer D. The shaft N drives one element of the aforesaiddifferential gear C and also one element of another differential gear Pby which the movement of the said shaft is added to the movement of ayaw receiver P and the resultant used for adjusting the disc of own shipanalyzer; the crank pin of this analyzer is adjusted in accordance withthe known speed of own ship. The yaw receiver comprises an electricmotor connected electrically to the ships gyro compass and controlledtherefrom,

Suitable clutches E and K are provided in the gearing between theaforesaid sliding elements D and D of the target analyzer and thedifferential gears E and K for the purpose of enabling the handles orknobs C and C to be adjusted to bring the pointer C into coincidencewith the point of intersection of the wires A and B without disturbingthe previous range and bearing rates set on the shafts G and M. Theseclutches may be interconnected by bell crank levers and links asindicated and may be operated by pulling and pushing the handles orknobs C and C suitable sliding couplings C and C being provided in theshafts operated thereby so as to maintain operative connection at alltimes. Alternatively the clutches may be of the electromagnetic type andbrought into and placed out of operation by the sliding movements of theknobs C and C".

In employing the apparatus in practice it is first necessary foroperators in the control positions on the ship to cause ranges to beplotted on the plotter H and bearings to be plotted on the plotter N,which ranges and bearings are due to the effects of the combinedmovements of target and own ships. Another operator will then set theown ships course and speed from observed data on the crank pincontrolling the sliders L F The angular disposition of the bar G inrelation to its zero position will at this time indicate or will be ameasure of the rate of change of range due to the movement of the ownship alone, since its angular disposition will be due solely to the ownship speed setting on the crank pin controlling the slider F The rangetuning handle H will now be operated to move the cursor bar G bodilywithout varying its angular disposition so that the bar remains parallelto its initial position. The bar G will be moved in this way until thepencil H is on the curve indicated by the points plotted on the plotterH Now the range plotting on the plotter H corresponds to ranges due tothe combined movements of both the target and own ship. The angulardisposition of the tangent to the curve of these plottings willtherefore indicate or will be a measure of the rate of change of rangedue to such combined movements. Therefore, the angular differencebetween the position of the cursor bar G and the position of the saidtangent will correspondingly indicate or will be a measure of the rateof change of range due solely to the movement of the target. It willtherefore be apparent that adjustment of the handle E (which adjusts therange rate wire A, operates the shaft G which in turn adjusts the memberH of the variable speed device, and actuates the member G and block G tovary the angle of the cursor bar) to move the bar G through the angulardifference referred to will bring the cursor bar into true tangentialrelation with the curve referred to, and since this difference isproportional solely to the rate of change of range due to the movementof the target ship, the range rate wire A will be actuated to indicatethe rate of change of range due to target course and speed.

In an exactly similar manner the bearing cursor bar M will be adjustedby the operation of the handle N and thereafter by operation of thehandle K to bring the cursor bar into true tangential relation with thecurve indicated by the points plotted on the plotter N", and to maintainit in such relation, whereby the linear bearing rate cross wire B willbe actuated in accordance with the rate of change of linear bearing dueto iii-d3; lithiblililb. actual! ilUUl target course and speed. Thesliders D D are adjusted initially (after disengaging the clutches E Kin accordance with the target course and speed indicated by the wires A,B, by moving the pointer (3 into coincidence with the point ofintersection of the wires A, B, by means of the handles C C whereby thecrank pin D is similarly adjusted and imparts the appropriate adjustmentto the sliders D D The slider D adjusted in accordance with own shipscourse and speed, a range element co-operating with the range rateindicator and actuated by said means 10 actuates the shaft G so as tovary the speed at in accordance with rate of change of range due 10which the member H of the variable speed gear to own ships movements, abearing element cois driven in accordance with the changing rateoperating with the bearing rate indicator and so as to cause the pencilH to trace out a curve actuated by said means in accordance with rate ofaverage range, or in other words to maintain of change of bearing due toown ships movethe pencil along the curve indicated by the plotted ments,means to apply additional movement to 15 points on the plotter H afterthe pencil has been the range element and to the bearing element toinitially set on the curve. The slider D also bring said elements intotangential relationship actuates the parts G, G G to vary the angularwith said curves so that the total movements of disposition of the barCi to maintain it in tansaid elements are in accordance with rate ofgential relation to the range curve. Similarly, change of range and ofbearing due to the 20 the bearing slider D will vary the rate at whichcombined movements of the target ship and own the member N is driven soas to maintain the ship, a target range rate indicating member pencil Non the bearing curve indicated by the adjusted by the means for applyingadditional point plotted on the plotter N and will vary the movement tothe range element, and a target angular disposition of the bar M bearingrate indicating member adjusted by the 2:3

The sliders D D are also connected to any means for applying additionalmovements to the suitable mechanism (not shown) which for exbearingelement. ample predicts or corrects target range and bear- O se in gunfi Control apparatus 011 a ing due to target course and speed. ship orother moving platform, a device as in Th lid F L are like ise connect dto claim 2wherein the target range indicating mem- 30 some mechanism(not shown) which for exher and target bearing indicating member arearample predicts or corrects range and bearing ranged djace t to e ot erand a alTanged due to own ship movement. to intersect and to move indiiferent directions When the mechanism has been adjusted as so thattheir point of intersection is an indicaabove described the analyzerswill, if the target tien o target Course and speed 35 course and speedand own ship speed remain or us in un fi Control pp tus 0 a constant,(1) automatically adjust the wires A, h p r o h m v n p m. a device m-B; (2) cause the button or pointer C to autoprising a range rateindicator which indicates a matically maintain coincidence with thepoint of C ve of as e ta ed rate f Change Of range intersection of thewires A, B; and (3) will mainwhich is due to the combined movements of a40 tain the cursor bars in tangential relation to the targetp and of np, a range Tate CUISOI curves referred to and the'pencils H N on said r,means for va y h n r i po ition curves, of the range rate cursor bar inaccordance with An operator will, however, constantly attend to han e or n e u to wn hip m v ment.

the handles C c so as to maintain the button means t pp y i nal m v m ns to the 4.3 or pointer C in coincidence with the point of r n r te c rr ar to in it in n en i l intersection when target course or speedvaries. relation with t Curve indicated y range Any suitable means otherthan those hereine ind to w y the total movement. pbefore described maybe employed for determinp ed o t range ate Cursor bar will be in a0- ingthe r t of ha g f range d bearing f r cordance with the rate of changeof range due to 50 efiecting the adjustment of the range rate wire eCombined movements of the target p and A and the linear bearing ate wir}3 of own ship, a target range rate indicator mem- What I claim anddesire to s cure by L tt her, and means to transmit the additional move-Patent of th U it d st t is;... ments applied to the cursor bar to thetarget 1. For use in gun fire control apparatus on a range rate memberwhereby the latter is moved 5.3 ship or other moving l tf d vi inaccordance with rate of change of range due prising an indicator whichindicates a curve of to e target p e. a be te indicator ascertained rateof change of a measu em t which indicates a curve of ascertained rate ofwhich rate of change i du t th bi d change of bearing which is due tothe combined movements of a target ship and of own ship, a movements ofthe target p and of wn S p. on cursor bar adjustable in relation to saidcurve, a bearing t urs bar, means t va y th means adjusted according tothe rate of change an l p i n f he rin rate cursor of said measurementdue solely to own ships bar in aCCOrdenee With rate of Change Omovements and which means move the cursor ea g due movements of Own palone,

bar in accordance with said rate of change due means t pp y d t onal vents to the 65 solely to own ships movement, a target rate incursor barto bring it into tangential relation dicating device, and additionalmeans for applywith the curve indicated by the bearing rate iningfurther movements to the cursor bar to bring d ater, a target bea a eihdieating memit into tangential relation with this curve which her, andmeans to transmit the additional moveadditional means simultaneouslyactuate the tarl cnts applied to the bearing rate cursor bar to (ll getrate indicating device in accordance with said the target bearing rateindicating member. further movements. 5. A device as in claim 4, whereinthe target 2. For use in gun fire control apparatus on a range memberand target bearing member are ship or other moving platform, a devicecomprisarranged adjacent to each other and to intersect ing a range rateindicator which indicates a and to move in different directions so thattheir 75 point of intersection is an indication of target course andspeed.

6. A device as in claim 4, wherein the means for transmitting theadditional movements applied to the bearing rate cursor bar to thetarget bearing rate indicating member include means for convertingangular bearing rate to linear bearing rate so as to move the targetbearing range indicating member in accordance with variation of linearbearing rate due to movements of the target ship.

7. A device as in claim 4 wherein the cursor bars are pivotally mountedand said device has means whereby the cursor bars can be moved bodily soas to remain parallel with respect to their initial positions, and meansto move the cursor bars about their pivots, which latter means alsoactuate the target range rate indicating member and the target bearingrate indicating member.

8. For use in gun fire control apparatus on a ship or other movingplatform, a device comprising a range rate indicator which indicates acurve of ascertained rate of change of range which is due to thecombined movements of a target ship and of own ship, a bearing rateindicator which indicates a curve of ascertained rate of change ofbearing which is due to the combined movements of target ship and of ownship, an analyzer which is adjusted in accordance with ascertainedcourse and speed of own ship, a range rate cursor bar, means to transfermovements to the range rate cursor bar from the analyzer to vary theangular disposition of the bar in accordance with the change of rangedue to own ships movements alone, means to apply additional movements tothe range rate cursor bar to bring it into tangential relation with thecurve indicated by the range rate indicator whereby the total movementapplied to the range rate cursor bar will be in accordance with rate ofchange of range due to the combined movements of the target and of ownship, a target range rate indicating member, and means to transmit theadditional movements applied to the cursor bar also to the target rangerate indicating member whereby the latter is moved in accordance withrate of change of range due to the target ship alone, a bearing ratecursor bar, means to vary the angular disposition of the cursor bar bytransmitting movements thereto from the analyzer in accordance with rateof change of bearing due to movements of own ship alone, means to applyadditional movement to the bearing rate cursor bar to bring it intotangential relation with the curve indicated by the bearing rateindicator, a target bearing rate indicating member, and means totransmit additional movements applied to the bearing rate cursor bar tothe target bearing rate indicating member whereby the latter is moved inaccordance with rate of change of bearing due to the target ship alone.

9. For use in gunfire control apparatus on a ship or other movingplatform, a device comprising a range rate indicator which indicates acurve of ascertained rate of change of range due to the combinedmovements of a target ship and of own ship, a bearing rate indicatorwhich indicates a curve of ascertained rate of change of bearing due tothe combined movements of a target ship and of own ship, an analyzerwhich is adjusted in accordance with own ship course and speed, a rangeelement co-operating with the range rate indicator and actuated by saidanalyzer in accordance with rate of change of range due to own shipsmovements, a bearing element co-operating with the bearing rateindicator and actuated by said analyzer in accordance with rate ofchange of bearing due to own ships movement, means to apply additionalmovements to the range element to bring it into tangential relationshipwith the range curve so that the total movements of said range elementare in accordance with rate of change of range due to the combinedmovements of target ship and own ship, means to apply additionalmovements to the bearing element to bring it into tangentialrelationship with the bearing curve so that the total movements of saidbearing element are in accordance with rate of change of bearing due tothe combined movements of target ship and own ship, a target range rateindicator member adjusted so that it indicates target speed by the meansfor applying additional movements to the range element, and a targetbearing range indicating member adjusted so that it indicates targethearing by the means for applying additional movements to the bearingelement.

10. Apparatus as in claim 9, having a second analyzer which is operatedin accordance with target course and speed, means to co-operate with thetarget range rate indicating member and target bearing rate indicatingmember and with said second analyzer whereby the latter can be adjustedin accordance with the indication of target course and speed given bysaid members, and variable speed means for actuating the range rateelement and bearing rate element which variable speed means are adjustedby connection to both said analyzers.

11. A device as in claim 9, having a second analyzer which is operatedin accordance with target course and speed, means to co-operate with thetarget range rate indicating member and target bearing rate indicatormember and with said second analyzer whereby the latter can be adjustedin accordance with the indication of target course and speed given bysaid members, variable speed means for continuously moving the saidrange and bearing elements without varying their angular disposition,and which variable speed means are adjusted by connection t the saidsecond analyzer.

12. For use in gunfire control apparatus on a ship or other movingplatform a device comprising a range plotter on which ascertained rangesdue to the combined movements of a target ship and of own ship areplotted to indicate a range curve, a bearing plotter on whichascertained bearings due to the combined movements of target ship and ofown ship are plotted to indicate a bearing curve, an analyzer which isadjusted in accordance with own ship course and speed, a range cursorbar co-operating with the range plotter, a pivotal support for the rangecursor bar, connections between said cursor bar and the analyzer wherebythe angular disposition of the cursor bar is varied in accordance withrate of change of range due to own ships speed, a manually adjustablemember for actuating said pivotal support so as to move the cursor barbodily without varying its inclination, a manually adjustable member forvarying the inclination of the cursor bar in addition to the movementimparted to the cursor bar from the analyzer, a target range rateindicator member, means for transmitting movement to said member fromthe second mentioned manually adjustable member, a

HCUEO llllO- bearing rate cursor bar, a pivotal support for said bearingrate cursor bar, a manually adjustable member for imparting movement tothe bearing rate cursor bar pivotal support so as to move the atterbodily without varying its inclination, means for transmitting movementfrom the analyzer to the bearing rate cursor bar for varying theinclination of the cursor bar in accordance with rate of change ofbearing due to own ships course said transmitting means including adevice for converting linear bearing rate movement to angular bearingrate movement, a manually operable member for applying additionalmovement to the bearing rate cursor bar through said device for varyingthe inclination of the bearing rate cursor bar, a target linear bearingrate indicating member, and means for transmitting movement from thelast mentioned manually operable member to the target linear bearingrate indicating member, th arrangement being such that the cursor barsare adjusted for inclination from the analyzer and are moved bodilyuntil their axes about which they pivot coincide with the curves on theplotters whereupon the differences between their positions and thetangents to the curves at said axes will be an indication of the rangeand bearing rates due to the movement of the target ship alone whereuponthe cursor bars will be moved through said difierences until they aretangential to said curves and simultaneously the target range rateindicating member and target linear bearing rate indicating member willboth be adjusted according to said respective differences.

13. For use in gunfire control apparatus on a ship or other movingplatform, a device comprising a range plotter on which ascertainedranges due to the combined movements of a target ship and of own shipare plotted to indicate a range curve, a bearing plotter on whichascertained bearings due to the combined movements of target ship and ofown ship are plotted to indicate a bearing curve, an own ship analyzerwhich is adjusted in accordance with own ship course and speed, a rangerate cursor bar co-operating with the range plotter, a support on whichthe range rate cursor bar is pivotally mounted, connections between saidcursor bar and the analyzer whereby the angular disposition of thecursor bar is varied according to rate of change of range due to ownships speed, a variable speed gear for driving the pivotal support so asto move the cursor bar bodily without varying its inclination, amanually adjustable member for actuating said support so as to impartadditional movements to the cursor bar without varying its inclination,a manually adjustable member for varying the in clination of the cursorbar in addition to the movement imparted to the cursor bar from theanalyzer, and for simultaneously varying the output speed of saidvariable speed gear, a target range rate indicator member, means fortransmitting movement to said target range rate indicating member fromthe second mentioned manually adjusting device, a bearing rate cursorbar, a support on which said bearing rate cursor bar is pivotallymounted, a bearing rate variable speed gear for actuating the bearingrate cursor bar support so as to move the bearing rate cursor bar bodilywithout varying its inclination, a manually adjustable member forimparting additional movement to the bearing rate cursor bar support,means for transmitting movement from the analyzer to the cursor bar forvarying the inclination of the cursor bar in accordance with rate of@Ediiiit ilUU change of bearing due to own ships ccurse'saidtransmitting means including a device for converting linear bearing ratemovement to angular bearing rate movement, a manually operable memberfor applying additional movement to the bearing rate cursor bar throughsaid device for varying the inclination of the cursor bar, a targetlinear bearing rate indicating member, andmeans for transmittingmovement from the last named manually operable member to the targetlinear bearing rate indicating member, a target analyzer which isadjusted in accordance with target course and speed, connections betweenthe target analyzer on the one hand through the converting device toboth the bearing rate variable speed gear and the bearing rate cursorbar on the other hand, whereby the bearing rate cursor bar iscontinuously adjusted according to the angular bearing rate due tomovements of the target and whereby the variable speed device'isadjusted so as to move the bearing rate cursor bar bodily, connectionsfor transmitting movements from the target analyzer in accordance withrate of change of range due to target speed to the range rate cursor barto vary the inclination thereof in accordance with the rate of change ofrange and also transmitting said movement to the range rate variablespeed gear to vary its output speed to the range rate cursor bar therebyvarying the speed at which the cursor bar is moved bodily, an indicatingdevice co-operating with the target range rate indicating member andwith the target linear bearing rate indicating member, means foradjusting said device in accordance with the movement of said members,and means for transmitting the movements of said adjusting means to thetarget analyzer to set the latter initially in accordance with thetarget course and speed indicated by said members.

14. For use in gunfire control apparatus on a ship or other movingplatform, a device comprising a range rate indicator which indicates acurve of ascertained rate of change of range due to the combinedmovement of target ship and of own ship, a bearing rate indicator whichindicates a curve of ascertained rate of change of bearing due to thecombined movement of a target ship and of own ship, an analyzer which isadjusted in accordance with own ships course and speed, a range elementco-operating with the range rate indicator and actuated by the analyzerin accordance with rate of change of range due to own ships movement, abearing element cooperating with the bearing rate indicator and actuatedby said analyzer in accordance with rate of change of bearing due to ownships movement, means to apply additional movement to the range elementand to the bearing element to bring said element into tangentialrelationship with said curve so that the total movement of said elementsare in accordance with rate of change of range and of bearing due to thecombined movement of target ship and own ship, a target range rateindicating member adjusted by the means for applying additional movementto the range element, and a target bearing rate member adjusted by themeans for applying additional movement to the bearing element.

15. For use in gunfire control apparatus on a ship or other movingplatform, a device comprising a range rate indicator which indicates acurve of ascertained rate of change of range which is due to thecombined movement of a target ship and of own ship, a bearing rateindicator which indicates a curve of ascertained rate of change ofbearing which is due to the combined movement of the target ship and ofown ship, a range rate element, means to move said element intaccordancewith rate of change of range due to own ship movement, means to movesaid element in accordance with rate of change of range due to movementof. the target alone, a member movable in accordance with the movementof the second mentioned means, a bearing rate element, means to move thebearing element in accordance with rate of change of bearing due to ownship alone, means to move said element in accordance with rate of changeof bearing due to movement of the target ship alone, an element movablein accordance with the movement of the second mentioned means for movingthe bearing rate element, said range-rate element and bearingrateelement being arranged to move at right angles to each other and tointersect so that their point of intersection indicates the targetcourse and speed.

16. A device as in claim 13 wherein the linear bearing rate indicatingmember and the range rate indicating member are arranged to moverelatively to each other so that the point of intersection of saidmembers will be an indication of target course and speed, and the saidmeans for adjusting the indicating device comprise a manually adjustablemember for adjusting the indicating device rotatably and anothermanually adjustable member for adjusting the indicating device radiallyby which two manually operable members the indicating device can bebrought into coincidence with the point of intersection referred to.

JOHH PERCQVAL WATSON.

